Transmission line transformers accept an input signal at an impedance Z.sub.IN and provide a corresponding output signal at an impedance Z.sub.OUT. In a "balun" type transformer, one of the signals is balanced (aka push-pull) and the other is single-ended.
High speed electronic circuits, such as microwave amplifiers and sub-nanosecond logic, often employ differential circuitry, and consequently operate with push-pull input signals. However, at these high frequencies, it is very difficult to maintain a signal in a truly balanced form. Mismatches, feedback, and other disturbances tend to induce a common mode signal on any balanced line. If the circuitry to which the signal is applied is to operate optimally, the signal must be restored to a truly balanced form. Thus, there is a need for a device that will reject common mode components from a nominally-balanced signal to restore it to a balanced state.
Further, conventional signal sources provide single-ended output signals. Before such signals can be applied to push-pull circuitry, they must first be converted to push-pull form.
In accordance with the present invention, a transmission line transformer is provided that can balance imperfectly balanced signals, and that can also convert a balanced input to a single-ended output.
The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawing.